Image compression apparatus, method and recording medium storing an image compression program

ABSTRACT

An image compression apparatus and method, and a carrier wave encoded with a computer readable control program having instructions for use by a computer, perform an image compression process. A compression level is determined for use in compressing a picture image to a predetermined target data amount by iteratively compressing a reduced version of the picture image in order to determine the compression level that is to be used to compress the picture image. First, a reduced-size picture image is created from the picture image that is to be compressed. A preliminary compression target data amount is then derived, for example, based on the target data amount, the data amount of the picture image and the data amount of the reduced-size picture image. The reduced-size picture image is then compressed using a compression level. The size of the resulting compressed reduced-size picture image is compared to the preliminary compression target data amount. The compression level is then adjusted (raised or lowered) and compression of the reduced-size picture image is repeated until the resulting compressed reduced-size picture image satisfies the preliminary compression target data amount. The compression level that ultimately is derived, is then used to compress the picture image. The resulting compressed picture image will then satisfy the predetermined target data amount.

RELATED PROVISIONAL APPLICATION

[0001] This nonprovisional application claims the benefit of ProvisionalApplication No. 60/057,680, filed Aug. 29, 1997.

INCORPORATION BY REFERENCE

[0002] The disclosure of the following priority application is hereinincorporated by reference: Japanese Patent Application No. 9-146365,filed Jun. 4, 1997.

BACKGROUND OF THE INVENTION

[0003] 1. Field of Invention

[0004] The present invention relates to an image compression apparatusthat compresses an image, particularly a picture image, and to acompression method and recording medium storing a computer readablecompression program.

[0005] 2. Description of Related Art

[0006] In recent years, there have been great advances in imagecompression technology to compress digital image compression signals.For example, compression methods such as the JPEG (Joint PhotographicExperts Group) and the MPEG (Moving Picture Experts Group) methods areknown, international standards for compressing digital still pictureimages and moving picture images.

[0007] These compression methods perform picture image compression byperforming the following processes in the order: Discrete CosineTransformation (DCT), followed by linear quantization, followed byvariable-length coding.

[0008] Picture image compression first divides the picture image intoblocks of, for example, 8×8 picture elements, and directly transformseach block of the picture image using DCT. The DCT separates the pictureimage signal into the portion that is necessary for viewing (thatportion of the picture image having low frequency components), and intothe portion that is not necessary for viewing (that portion of thepicture image having high frequency components).

[0009] Next, quantization is performed by means of frequency weightedquantization. Frequency weighted quantization is a method that quantizesby changing the quantization amount in accordance with the frequency.Since the picture image data is transformed into frequency coefficientsby the DCT, for example, the quantization amount is increased for thehigh frequency components that are not necessary for viewing, therebyreducing the data amount. The quantization amount is made smaller forthe low frequency components that are necessary for viewing, therebycontrolling the deterioration of the picture image.

[0010] Next, variable length code (VLC) such as, for example, Huffmanencoding or so forth is applied. Huffman encoding, by assigning variablelength code according to the frequency by which data is generated,encodes by assigning code with the shortest bit length to the data withthe highest frequency of occurrence, thereby reducing the data amount.

[0011] With the picture image compression processing described above,the compression efficiency varies according to the amount of spatialredundancy of the particular picture image. In other words, a pictureimage having high spatial redundancy (for example, a natural pictureimage with low contrast) is appropriate for picture image compressionbecause it can attain high compression efficiency. On the other hand, apicture image having little or no spatial redundancy (for example,computer graphics with high contrast) is not suitable for picture imagecompression because the compression efficiency (using JPEG or MPEG, forexample) is low.

[0012] Depending upon the amount of this type of spatial redundancy, thepost-compression file size varies greatly even when undergoing thecompression process at the same compression level.

[0013] The electronic still camera is one primary example of a devicethat can suffer from this ill effect. The electronic still cameracompresses a photographed picture image, input by means of a CCD, andrecords it in non-volatile memory. Normally, it is possible to compressand record several 10 s of photographic picture images (e.g., 20-60images). However, when the post-compression file size varies greatly foreach photographic picture image, it becomes impossible to know withcertainty how many picture images can be recorded in a particularmemory.

[0014] For this purpose, electronic still cameras have been proposed tounify and record the post-compression file size. With these cameras, apicture image undergoes compression processing so as to become astandard file size. For example, in the case of compressing aphotographic picture image so as to have a unified file size of 100 KB,first, compression processing is performed at a certain compressionlevel. If the compression result is larger than 100 KB, the compressionlevel is raised and the compression process is repeated. If thecompression result is smaller than 100 KB, then the compression level islowered and the compression process is repeated.

[0015] By repeating the compression process by appropriately changingthe compression level in this way, the photographic picture image iscompressed to a standard file size. However, generally, since the filesize of a photographic picture image is large, the computation time ofcompression processing is increased, creating a problem in that a longtime is required until the photographic picture image can be compressedto the standard size.

SUMMARY OF THE INVENTION

[0016] The invention relates to an image compression apparatus andmethod, and to a carrier wave (that can be recorded, for example, on arecording medium) encoded with a computer readable control programhaving instructions for use by a computer to perform the imagecompression process. According to one aspect of the invention, acompression level is determined for use in compressing a picture imageto a predetermined target data amount by iteratively compressing areduced version of the picture image in order to determine thecompression level that is to be used to compress the picture image.

[0017] First, a reduced-size picture image is created from the pictureimage that is to be compressed. The reduced-size picture image has some,but not all, of the picture elements from the picture image. Thus, thereduced-size picture image has fewer picture elements than the pictureimage. T he reduced-size picture image can be created by extracting afield picture image from the full-size (or frame) picture image and/orby producing a thumbnail picture image from the full-size picture image.

[0018] A preliminary compression target data amount is then derived, forexample, based on the target data amount, the data amount of the pictureimage and the data amount of the reduced-size picture image. Forexample, the preliminary compression target data amount can be derivedby multiplying the target data amount by a ratio between the size of thereduced-size picture image and the full-size picture image.

[0019] The reduced-size picture image is then compressed using acompression level. The size of the resulting compressed reduced-sizepicture image is then compared to the preliminary compression targetdata amount. The compression level is then adjusted (raised or lowered)and compression of the reduced-size picture image is repeated until theresulting compressed reduced-size picture image satisfies thepreliminary compression target data amount.

[0020] The compression level that ultimately is derived, is then used tocompress the picture image. The resulting compressed picture image willthen satisfy the predetermined target data amount.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The invention will be described in conjunction with the followingdrawings in which like reference numerals designate like elements andwherein:

[0022]FIG. 1 is a high-level functional diagram of one aspect of theinvention;

[0023]FIG. 2 is a block diagram of a camera according to a firstembodiment of the invention;

[0024]FIG. 3 is a perspective view of the FIG. 2 camera;

[0025]FIG. 4 is a flow chart of a main routine performed by a camera ofthe first embodiment;

[0026]FIG. 5 is a flow chart of a release routine performed by a cameraof the first embodiment;

[0027]FIG. 6 is a flow chart of a recording routine performed by acamera of the first embodiment;

[0028]FIG. 7 is a flow chart of a read routine performed by a camera ofthe first embodiment;

[0029]FIG. 8 illustrates the relationship between the compression leveland the expected compression ratio;

[0030]FIG. 9 illustrates the picture image compression process of thefirst embodiment;

[0031]FIG. 10 is a block diagram of a camera according to a secondembodiment of the invention;

[0032]FIG. 11 is a block diagram of a camera according to a thirdembodiment of the invention;

[0033]FIG. 12 is a flow chart of a main routine performed by the cameraof the third embodiment;

[0034]FIG. 13 is a flow chart of a release routine performed by thecamera of the third embodiment;

[0035]FIG. 14 is a flow chart of a recording routine performed by thecamera of the third embodiment;

[0036]FIG. 15 is a first part of a flow chart of a single-view displayroutine;

[0037]FIG. 16 is a second part of a flow chart of the single-viewdisplay routine;

[0038]FIG. 17 illustrates thumbnail picture image creation; and

[0039]FIG. 18 illustrates the thumbnail picture image selection processand a plurality of thumbnail picture images displayed on a displayscreen.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0040]FIG. 1 is a high-level representation of one aspect of theinvention. An electronic camera includes a number of functional portionsor sub-sections, referred to in FIG. 1 as “means.” As will become clearfrom the ensuing description, each means is not necessarily a separateor separable unit or component of the camera. There can be overlapbetween the actual structure and software of the camera that performs(or corresponds to) the various means. For example, a singlemicroprocessor can function as parts of (or all of) more than one of theillustrated means. Alternatively, it is possible to use separate,dedicated microprocessors for each means that relies on microprocessorcontrol.

[0041] One aspect of the invention relates to a picture imagecompression apparatus that compresses the data of a picture image to apredetermined target data amount. A picture image creation means 1creates, from a picture image (e.g., a digital image input through aCCD), a reduced-size picture image having a reduced number of pictureelements compared to the picture image. A data amount determinationmeans 2 derives, using the target data amount, a preliminary compressiontarget data amount, which is the target data amount of the reduced-sizepicture image. A preliminary compression means 3 derives a compressionlevel when the data amount of the compressed reduced-size picture imagematches the preliminary compression target data amount. Preliminarycompression means 3 derives the compression level by repeating acompression operation after changing the compression level forcompressing the data of the reduced-size picture image until thepreliminary compression target data amount is reached. Then, compressionmeans 4 compresses the data of the picture image to the target dataamount according to the compression level derived from the preliminarycompression means 3.

[0042] The picture image creation means 1 can create a field pictureimage as the reduced-size picture image from a frame picture image. Thepicture image creation means I can create a thumbnail picture image asthe reduced-size picture image in order to display the thumbnail pictureimage in a single-view display.

[0043] Another aspect of the invention relates to a method ofcompressing a picture image and to a carrier wave encoded with acomputer readable program that includes instructions for causing acomputer to compress a picture image as detailed above. The carrier wavecan be recorded on a recording medium such as, for example, a CD ROM.The program includes a number of instructions. One instruction is tocreate from a picture image, a reduced-size picture image having areduced number of picture elements compared to the picture image.Another instruction is to derive a preliminary compression target dataamount, which is the post compression data amount of the reduced-sizepicture image. This is derived using a predetermined target data amount,which is the post-compression data amount of the picture image, and bycomparing the data amount of the picture image and the data amount ofthe reduced-size picture image. Another instruction is to derive acompression level when the post-compression data amount of thecompressed reduced-size image matches the preliminary compression targetdata amount. The compression level is derived by repeating compressionafter changing the compression level for the data of the reduced-sizepicture image. A final instruction is to compress the data of thepicture image to the target data amount according to the derivedcompression level.

[0044] With the picture image compression apparatus and method outlinedabove, first the picture image creation means 1 creates the reduced-sizepicture image, which has a reduced number of picture elements from thepicture image. This is done before compressing the data of the pictureimage.

[0045] The data amount determination means 2 then derives thepreliminary compression target data amount, which is the target dataamount for compression of the reduced-size picture image. Thepreliminary compression target data amount is derived from the targetdata amount of the picture image according to the ratio of the pictureimage to the reduced-size picture image. However, the data amountdetermination means 2 may also derive this amount directly, or it may becalculated by another means and set in advance into the data amountdetermination means 2.

[0046] The preliminary compression means 3 changes the compression levelrelative to the data of the reduced-size picture image, and repeatsexecution of the compression process (of the reduced-size picture image)until it derives the final compression level, which is the compressionlevel at the time that the data of the reduced-size picture image iscompressed to a size corresponding to the preliminary compression targetdata amount.

[0047] The compression means 4 executes, according to the finalcompression level, the main compression (of the picture image) so thatthe data of the picture image becomes compressed to the predeterminedtarget data amount.

[0048] According to one option, the picture image creation means 1extracts the field picture image as a reduced-size picture image fromthe frame picture image by means of a thinning process of the pictureimage data. For example, every other scan line can be ignored (thinnedout).

[0049] According to another option, the picture image creation means 1creates the reduced-size picture image by producing a thumbnail pictureimage in order to display the picture image as a single-view display.

[0050] Embodiments of the present invention are described hereafter withreference to the drawings. In the present embodiment, an example of anelectronic still camera will be given as a description of a device thatuses the picture image compression apparatus of the present invention.FIG. 2 is a block diagram of an electronic still camera that is a firstembodiment of the invention. FIG. 3 is a perspective view of the cameraof the first embodiment.

[0051] In FIG. 2, the main body 21 is connected to a camera component22. The internal components of the camera component 22 include aphotographic lens 23 and a CCD sensor 24 arranged in a position toreceive transmitted light of the photographic lens 23. Thephoto-electric signal of the CCD sensor 24 is input, through an A/Dconverter 25, into a picture image memory 26, which is arranged withinthe main body 21.

[0052] The output of the picture image memory 26 is input through anencoder 27 into a video selection switch 28. The output of the videoselection switch 28 is input into a monitor 29 or into a video terminal30.

[0053] Meanwhile, the input/output terminal of the picture image memory26 is connected to a first input/output terminal of a picture imageprocessing circuit 31, which is arranged within the main body 21. Asecond input/output terminal of the picture image processing circuit 31is connected to an input/output terminal of a picture image processingmemory 32.

[0054] The picture image processing memory 32 is connected to a flashmemory 35 through a JPEG circuit 33 and a data transfer component 34.Flash memory 35 can be a card type of memory that has the ability to beattached and removed freely from the main body 21.

[0055] Picture image data can be transferred in both directions betweenthe picture image processing memory 32 and the flash memory 35.

[0056] CPU 36 also is arranged within the main body 21. The controlsignal of the CPU 36 is input into the CCD sensor 24, the encoder 27,the picture image processing circuit 31, the JPEG circuit 33 and thedata transfer component 34. In addition, the output signals of the JPEGcircuit 33, the data transfer component 34 and the operation switch 37are input into the CPU 36.

[0057] The corresponding relationship between the high-levelrepresentation of FIG. 1 and the first embodiment is as follows. Thepicture image creation means 1 corresponds to the CCD sensor 24, the A/Dconverter 25 and the picture image memory 26. The data amountdetermination means 2 corresponds to the CPU 36. The preliminarycompression means 3 corresponds to the JPEG circuit 33. The compressionmeans 4 also corresponds to the JPEG circuit 33.

[0058] A description of the operation of the first embodiment isprovided hereafter, with reference to the drawings. FIG. 4 through FIG.7 are flow charts describing the operation of the first embodiment. Inaddition, FIG. 9 illustrates the picture image compression process ofthe present embodiment.

[0059] When the power switch (not shown in the figure) is switched ON,the CPU 36 executes the following operation according to the camerasequence program stored in internal ROM. The CPU 36 initializes thesystem after clearing the picture image memory 26 and the picture imageprocessing memory 32. The start photography command is input from theCPU 36 into the CCD sensor 24 and photography begins (step S1 of FIG.4).

[0060] The photographic object obtained through the photographic lens 23is formed on the CCD sensor 24 and converted photo-electrically. Thephoto-electric signal, by reading every other scanning line includes twofield signals in a time series as is well known. In other words, an evennumber field signal and an odd number field signal that have a reducednumber of picture elements in the vertical direction are output. Thesesignals together comprise, in the same manner as the video signal, oneframe of image data. The one frame has two fields, one with an evennumber field signal and one with an odd number field signal.

[0061] The A/D converter 25 increases the width of the even number fieldsignal and the odd number field signal respectively, and then convertsthem to a digital video signal. In the picture image memory 26, thedigital video signal is accumulated in the order received, and hence theeven number field picture image and the odd number field picture imageare created.

[0062] The encoder 27 chronologically reads the even number fieldpicture image and the odd number field picture image that are stored inthe picture image memory 26, and then D/A converts them to an analogprojected image signal, and outputs them to the video terminal 30 or tothe monitor 29 that is selected by the video selection switch 28.

[0063] In this instance, the monitor 29 is selected. The monitor 29,which is, for example, a liquid crystal display monitor, A/D convertsthe analog projected image signal, combines the even number fieldpicture image and the odd number field picture image, integrates theframe picture image and performs display by means of the active matrixmethod.

[0064] Through the operation described above, the picture image istaken-in regularly and is chronologically displayed on the monitor 29.

[0065] In this state, the CPU 36 determines whether the release switchSW1 of the operation switch 37 has been pressed. If the release switchSW1 is pressed (step S2 in FIG. 4), the following release routine isexecuted (step S3 in FIG. 4).

[0066] The CPU 36 outputs the stop output command of the analogprojected image signal to the encoder 27. The encoder 27 stops readingthe field picture image that is stored in the picture image memory 26,and temporarily stops the output of the analog projected image signal tothe monitor 29 (step S11 in FIG. 5). Next, at the moment that therelease switch SW1 is pressed, the image formed on the CCD sensor 24 isphoto-electrically converted and accumulated to the picture image memory26 through the A/D converter 25 (step S 12 in FIG. 5). The CPU 36outputs the restart output command of the analog projected image signalto the encoder 27, and the encoder 27 reads the even number fieldpicture image and the odd number field picture image that are stored inthe picture image memory 26, and A/D converts each to the analogprojected image signal, and then outputs this to the monitor 29 (stepS13 in FIG. 5).

[0067] According to the operation described above, the operator has theability to take in a picture image at the moment there is a photographicopportunity by pressing the release switch SW1.

[0068] Next, a description of the operation that records the takenpicture image into the flash memory 35 will be described hereafter.

[0069] The CPU 36 determines whether the recording switch SW2 of theoperation switch 37 is pressed. When the recording switch SW2 is pressed(step S4 of FIG. 4), the following recording routine is executed (stepS5 in FIG. 4).

[0070] The picture image processing circuit 31, in accordance with thefield picture image reading command supplied from the CPU, reads one ofthe fields (either the even number field picture image or the odd numberfield picture image) that are accumulated in the picture image memory26, and transfers it to the picture image processing memory 32 (step S21of FIG. 6).

[0071] The CPU 36, for example, can be set in advance so as to compressa several MB (megabyte) frame picture image to a target data amount ofabout 100 KB (kilobytes). In addition, since the field picture imagebecomes the data amount of ½ of the frame picture image, the CPU 36 canbe set in advance so as to compress the field picture image to apreliminary compression target data amount of 50 KB. The JPEG circuit 33repeats the compression process until the field picture image that isstored in the picture image processing memory 32 becomes the preliminarycompression target data amount.

[0072] In this instance, a description of a specific numerical valuewill be given relative to the preliminary compression process. Forexample, the data amount of the field picture image is 500 KB (with aframe picture image of 1 MB). Stored in advance in the internal ROM ofthe JPEG circuit 33 is the relationship between the compression ratiothat is expected (hereafter referred to as the expected compressionratio) and the compression level that the standard picture image issubject to. A graph of this is shown in FIG. 8. In this instance, theexpected compression ratio that corresponds to the compression levels 1through 99 is indicated.

[0073] A preliminary compression target data amount and a preliminarycompression initiation command are transferred from the CPU 36 to theJPEG circuit 33. The JPEG circuit 33, in accordance with such command,reads the field picture image that is stored in the picture imageprocessing memory 32 and begins the compression. In particular, JPEGcircuit 33 reads the data amount of the field picture image that isstored in the picture image processing memory 32 and compresses suchdata amount so that it matches the preliminary compression target dataamount. In this instance, since a 500 KB data amount must be compressedso as to become 50 KB, first, compression is performed at a compressionlevel of 30 (expected compression ratio 10%). The picture imagecompression is performed by performing the following procedure in thefollowing order: DCT, followed by linear quantization, followed byvariable length coding (step S22 in FIG. 6). JPEG circuit 33 repeats thecompression process by changing the compression level until thecompression result is within a range of 50 KB± an allowable value,thereby deriving the compression level when arriving within this range(steps S23 and S24 of FIG. 6).

[0074] For example, when the compression result is 40 KB, since thecompression level is too large and there is the possibility that thepicture image will deteriorate upon reproduction, the compression levelis lowered. In this instance, this is derived by the followingexpression (1):

(Expected compression ratio for the next time)=(the expected compressionratio of the previous time)×(preliminary compression target dataamount)/(data amount of the compression result of the previous time)  (1)

[0075] According to expression (1), an expected compression ratio forthe next time is computed to be 12.5%, and the JPEG circuit 33 perfonnscompression again at the compression level that corresponds to theexpected compression ratio. It then determines whether the compressionresult has become 50 KB.

[0076] In addition, when the compression result is 60 KB, since thecompression level is too small, an expected compression ratio of 8.3% iscomputed. Then, the compression is performed again at the compressionlevel that corresponds to this expected compression ratio, and it isdetermined whether the compression result has become 50 KB.

[0077] The change of the compression level can be executed by changingthe quantization amount. More specifically, in the internal ROM of theJPEG circuit 33, a quantization table of differing quantization amountsis prepared in advance for each compression level, and this quantizationtable is appropriately used.

[0078] The JPEG circuit 33 repeats the feed back process describedabove, and the compression level that compresses the field picture imageto the preliminary compression target data amount is derived andtransferred to the CPU 36. The CPU 36 stores that compression level inthe internal memory (step S25 of FIG. 6).

[0079] Next, the picture image processing circuit 31, by means of theframe picture image creation command from the CPU 36, reads the evennumber field picture image and the odd number field picture image thatare accumulated in the picture image memory 26, and integrates the framepicture image from the combined two field picture images (step S26 ofFIG. 6)

[0080] The picture image processing circuit 31 transfers the framepicture image to the picture image processing memory 32. The JPEGcircuit 33, according to the start main compression command from the CPU36, performs the compression by reading the frame picture image from thepicture image processing memory 32. At this time, the JPEG circuit 33,according to the compression level derived by the preliminarycompression, compresses the frame picture image (step S27 of FIG. 6).Since the extent of the spatial redundancy of the frame picture imageand the field picture image are nearly identical, the compression levelof the field picture image can comply with the frame picture image.Accordingly, when compression occurs at this compression level, theframe picture image is compressed to the target data amount.

[0081] The frame picture image that is compressed to the target dataamount is read and recorded to the flash memory 35 through the datatransfer component 34 as a compressed picture image file (step S28 ofFIG. 6). At this time, the compression level at the time of compressionis recorded in the header area of the compressed picture image file,together with the identification name of the file.

[0082] According to the operation described above, a taken picture imagecan be recorded to the flash memory 35.

[0083] A description of the operation for reading and reproducing apicture image that has been recorded in the flash memory 35 will now beprovided. The CPU 36 determines whether the read switch SW3 of theoperation switches 37 is pressed, and when the read switch SW3 ispressed (step S6 of FIG. 4), the read routine, to be describedhereafter, is executed (step S7 of FIG. 4).

[0084] As an example, assume the four compressed picture image files athrough d are recorded in the flash memory 35. One of the compressedpicture image files is selected by use of the picture image selectionswitch SW4. The CPU 36 reads the selected compressed picture image filefrom the flash memory 35 through the data transfer component 34 andtransfers it to the picture image processing memory 32 (step S31 of FIG.7). At this time, the CPU 36 reads the compression level used at thetime of compression from the header area of the compressed picture imagefile.

[0085] The start expansion (decompression) command and the compressionlevel information of the compressed picture image file are transferredfrom the CPU 36 to the JPEG circuit 33, where the JPEG circuit 33performs the expansion process of the compressed picture image accordingto the following procedure in the following order: variable lengthdecoding, followed by reverse quantization, followed by reverse DCT(step S32 of FIG. 7). At this time, the JPEG circuit 33, for reversequantization, executes the expansion process that corresponds to thecompression level used by the quantization table that was used at thetime of quantization.

[0086] The frame picture image that is restored (decompressed) by theJPEG circuit 33 is stored in the picture image processing memory 32. TheCPU 36 outputs the stop output command of the analog projected imagesignal to the encoder 27. The encoder 27, according to such command,stops the reading of the field picture image that is stored in thepicture image memory 26, and the output of the analog projected imagesignal is stopped to the monitor 29 (step S33 of FIG. 7).

[0087] The picture image processing circuit 31 divides the restoredframe picture image into an even number field picture image and an oddnumber field picture image, thereby creating two picture image fields,which are transferred to the picture image memory 26 (step S34 of FIG.7). The encoder 27, by means of the restart output command of the analogprojected image signal from the CPU 36, reads the even number fieldpicture image and the odd number field picture image that are stored inthe picture image memory 26, and D/A converts these to a sequentialanalog projected image signal, which is output to the monitor 29 (stepS35 of FIG. 7).

[0088] According to the process described above, the compressed pictureimage is restored and displayed on the monitor 29. In this way, theelectronic still camera of the first embodiment derives the compressionlevel by performing preliminary compression by way of a field pictureimage, which has a small data amount. Then, compression of the framepicture image is performed with the derived compression level.Accordingly, since compression is never repeated with a frame pictureimage, which has a large data amount, the load on the hardware can bereduced, and the time until the frame picture image is compressed to thetarget data amount can be shortened.

[0089] More specifically, with the electronic still camera of thepresent embodiment, since a photographic picture image can be compressedand recorded in an extremely short period of time, it becomes possibleto improve successive photography speed when performing successivephotography.

[0090] In the first embodiment, the output of the CCD sensor 24 was thefield picture image, however, in a second embodiment, the output of theCCD sensor 24 will be the frame picture image. Furthermore, the pictureimage compression process is performed according to a program that isstored in a recording medium (ROM card 45, see FIG. 10).

[0091]FIG. 10 is a block diagram of the second embodiment. In FIG. 10, amain body 21 is attached to a camera component 22. Within the cameracomponent 22 are a photographic lens 23 and a CCD sensor 24, which isarranged in a position to receive transmitted light of the photographiclens 23. The photo-electric signal of the CCD sensor 24 is input,through the A/D converter 25, into the picture image memory 26 arrangedwithin the main body 21.

[0092] The output of the picture image memory 26 is input into thepicture image processing circuit 38, and a first input/output terminalof the picture image processing circuit 38 is connected to the videomemory 39. Further, the output of the video memory 39 is input into thevideo selection switch 28 through the encoder 27. The output of thevideo selection switch 28 is input into the monitor 29 or the videoterminal 30.

[0093] The second input/output terminal of the picture image processingcircuit 38 is connected to the flash memory 35 through the picture imageprocessing memory 32, the JPEG circuit 33 and the data transfercomponent 34. Picture image data is transferred in both directionsbetween the picture image processing circuit 38 and the flash memory 35.

[0094] Further, the CPU 40 is arranged within the main body 21, and thecontrol output of the CPU 40 is input into the CCD sensor 24, theencoder 27, the JPEG circuit 33, the data transfer component 34 and thepicture image processing circuit 38. In addition, the CPU 40 receivesthe output signals of the JPEG circuit 33, the data transfer component34 and the operation switches 37.

[0095] Further, in the main body 21, the ROM card 45 is arranged so asto be able to be freely removed and attached. The output of the ROM card45 is input into the data transfer component 34. In addition, a cameracontrol program is stored in the ROM card 45.

[0096] The corresponding relationship between the high-levelrepresentation of the invention in FIG. 1 and the second embodiment isas follows. The picture image creation means 1 corresponds to thepicture image processing circuit 38 and the video memory 39. The dataamount determination means 2 corresponds to the CPU 40. The preliminarycompression means 3 corresponds to the JPEG circuit 33. The compressionmeans 4 also corresponds to the JPEG circuit 33. The picture imagecompression processing program is stored on ROM card 45.

[0097] A description of the operation of the second embodiment is nowprovided.

[0098] When the power switch (not shown in the figure) is switched ON,the CPU 40, through the data transfer component 34, reads the cameracontrol program that is stored in the ROM card 45 and executes thefollowing operations according to the program.

[0099] The CPU 40 initializes the system after clearing the pictureimage processing memory 32 and the video memory 39. The startphotography command is input from the CPU 40 into the CCD sensor 24 andphotography begins. The photographic object obtained through thephotographic lens 23 is formed on the CCD sensor 24 and convertedphoto-electrically. The photo-electric signal is read in sequence andconverted into a digital video signal by the A/D converter 25. In thepicture image memory 26, the digital video signal is accumulated in theorder received, thereby creating the frame picture image.

[0100] The picture image processing circuit 38 divides the frame pictureimage that is stored in the picture image memory 26 into an even numberfield picture image and an odd number field picture image by reading thepicture element of every other scanning line. This is illustrated inFIG. 9.

[0101] The even number field picture image and the odd number fieldpicture image that were divided by the picture image processing circuit38 are accumulated and stored in sequence in the video memory 39.

[0102] The encoder 27 sequentially reads the even number field pictureimage and the odd number field picture image that are stored in thevideo memory 39, and then D/A converts them to an analog projected imagesignal, and outputs them to the video terminal 30 or the monitor 29 thatis selected by the video selection switch 28. In this instance, themonitor 29 is selected.

[0103] Through the operation described above, when the power switch isswitched ON, the picture image is taken-in regularly and sequentiallydisplayed on the monitor 29. In this state, the CPU 40 determineswhether the release switch SW1 of the operation switches 37 has beenpressed. If the release switch SW1 is pressed, the following releaseroutine is executed.

[0104] The CPU 40 outputs the stop output command of the analogprojected image signal to the encoder 27. The encoder 27 stops, inaccordance with such a command, reading the field picture image that isstored in the video memory 39, and temporarily stops the output of theanalog projected image signal to the monitor 29. Next, at the momentthat the release switch SW1 is pressed, the image formed on the CCDsensor 24 is accumulated and stored to the picture image memory 26through the A/D converter 25. The picture image processing circuit 38divides the frame picture image that is stored in the picture imagememory 26 into an even number field picture image and an odd numberfield picture image by reading the picture element of every otherscanning line, and the two picture image fields are transferred to thevideo memory 39.

[0105] The CPU 40 outputs the restart output command of the analogprojected image signal to the encoder 27, and the encoder 27 reads theeven number field picture image and the odd number field picture imagethat are stored in the video memory 39, and D/A converts each of theseto an analog projected image signal, and then outputs it to the monitor29.

[0106] According to the operation described above, the operator has theability to take in a picture image at the moment there is a photographicopportunity by pressing the release switch SW1.

[0107] A description of the operation that records the taken pictureimage into the flash memory 35 is now described. The CPU 40 determineswhether the recording switch SW2 of the operation switches 37 ispressed, and when the recording switch SW2 is pressed, the followingrecording routine is executed.

[0108] Picture image processing circuit 38, according to the fieldpicture image creation command from the CPU 40, divides the framepicture image that is stored in the picture image memory 26 into an evennumber field picture image and an odd number field picture image andstores them in the video memory 39. Picture image processing circuit 38,according to the field picture image reading command from the CPU 40,selects one of the two fields from the video memory 39, and transfers itto the picture image processing memory 32. The CPU 40, for example, isset in advance so as to compress a several MB frame picture image to atarget data amount of about 100 KB. In addition, since the field pictureimage is the data amount of ½ of the frame picture image, the CPU 40 isset in advance so as to compress the field picture image to apreliminary compression target data amount of 50 KB.

[0109] Although the preliminary compression target data amount is set inadvance in the CPU 40 as an alternative, the CPU 40 may also be set upto read the data amount of the field picture image and the frame pictureimage and compute directly by way of the expression (preliminarycompression target data amount)=(target data amount)×(data amount of thefield picture image)/(data amount of the frame picture image).

[0110] The JPEG circuit 33 repeats the compression process until thefield picture image that is stored in the picture image processingmemory 32 becomes the preliminary compression target data amount.Furthermore, since the specifics of the preliminary compression thattakes place in the picture image processing memory 32 and the JPEGcircuit 33 has already been described above in the first embodiment,further explanation will be omitted here. The preliminary compression isperformed of the field picture image, and when the compression level isdetermined, the picture image processing circuit 38 transfers the framepicture image stored in the picture image memory 26 to the picture imageprocessing memory 32 by following the frame picture image readingcommand from the CPU 40.

[0111] The JPEG circuit 33, according to the start ma-n compressioncommand from the CPU 40, performs compression by reading the framepicture image from the picture image processing memory 32. At this time,the JPEG circuit 33 compresses the frame picture image in accordancewith the compression level derived by the preliminary compression. Theframe picture image that is compressed to the target data amount is readand recorded to the flash memory 35 through the data transfer component34 as a compressed picture image file.

[0112] According to the operation described above, a taken picture imagecan be recorded to the flash memory 35.

[0113] A description of the operation for reading and reproducing apicture image that has been recorded in the flash memory 35 is nowprovided. The CPU 40 determines whether the read switch SW3 of theoperation switches 37 is pressed, and when the read switch SW3 ispressed, the read routine to be described hereafter is executed.

[0114] A compressed picture image file is read from the flash memory 35,and is expanded to the frame picture image by the JPEG circuit 33. Sincethe specifics of the operation to store into the picture imageprocessing memory 32 have already been described in the firstembodiment, further explanation will be omitted here.

[0115] The CPU 40 outputs the stop output command of the analogprojected image signal to the encoder 27. The encoder 27, according tosuch command, stops the reading of the field picture image that isstored in the video memory 39. The picture image processing circuit 38divides the frame picture image that is stored in the picture imageprocessing memory 32 into an even number field picture image and an oddnumber field picture image, thereby creating two picture image fieldsthat are transferred to the video memory 39.

[0116] The encoder 27, by means of the restart output command of theanalog projected image signal from the CPU 40, reads the even numberfield picture image and the odd number field picture image that arestored in the video memory 39, and D/A converts them to a sequentialanalog projected image signal where it is output to the monitor 29.

[0117] According to the process described above, the compressed pictureimage is restored and displayed on the monitor 29. The second embodimenthas the same result as the first embodiment.

[0118] In a third embodiment, preliminary compression will be performedby using a thumbnail picture image, rather than a field picture image.FIG. 11 is a block diagram of the third embodiment.

[0119] In FIG. 11, a main body 21 is attached to a camera component 22.Within the camera component 22 are a photographic lens 23 and a CCDsensor 24, which is arranged in a position to receive transmitted lightof the photographic lens 23. The photo-electric signal of the CCD sensor24 is input, through the A/D converter 25, into the picture image memory26, which is arranged within the main body 21.

[0120] The output of the picture image memory 26 is input into thepicture image processing circuit 38. The output terminal of the pictureimage processing circuit 38 is connected to the input terminal of thevideo memory 39. Further, the output of the video memory 39 is inputinto the video selection switch 28 through the encoder 27. The output ofthe video selection switch 28 is input into the monitor 29 or the videoterminal 30.

[0121] The input/output terminal of the picture image memory 26 isconnected to the input/output terminal of the picture image processingcircuit 41, which is arranged within the main body 21. The picture imageprocessing circuit 41 transfers picture image data in both directionsbetween the picture image processing memory 32 and the frame memory 42.The picture image processing memory 32 is connected to the flash memory35 through the JPEG circuit 33 and the data transfer component 34.Picture image data is transferred in both directions between the pictureimage processing memory 32 and the flash memory 35.

[0122] Further, the CPU 43 is arranged within the main body 21. Thecontrol output of the CPU 43 is input into the CCD sensor 24, theencoder 27, the JPEG circuit 33, the data transfer component 34 and thepicture image processing circuit 41. The output signals of the JPEGcircuit 33, the data transfer component 34 and the operation switches 44are input into the CPU 43.

[0123] Further, in the main body 21, the ROM card 45 is arranged so asto be able to be freely removed and attached. The output of the ROM card45 is input into the data transfer component 34. In addition, in thisROM card 45 is stored the camera control program.

[0124] The corresponding relationship between the high-levelrepresentation of the invention in FIG. 1 and the third embodiment is asfollows. The picture image creation means 1 corresponds to the pictureimage processing circuit 41 and the frame memory 42. The data amountdetermination means 2 corresponds to the CPU 43. The preliminarycompression means 3 corresponds to the JPEG circuit 33. The compressionmeans 4 also corresponds to the JPEG circuit 33.

[0125]FIG. 12 through FIG. 16 are flow charts describing the operationof the third embodiment. A description of the operation of the thirdembodiment is provided hereafter with reference to the figures.

[0126] When the power switch (not shown in the figure) is switched ON,the CPU 43, through the data transfer component 34, reads the cameracontrol program stored in the ROM card 45 and executes the followingoperation according to such program.

[0127] After clearing the picture image memory 26, the picture imageprocessing memory 32, the video memory 39, and the frame memory 42, theCPU 43 initializes the system (step S41 in FIG. 12).

[0128] The switch SW5 of the operation switches 44 is a mode switch thatswitches between the photographic mode and the single-view display mode.The CPU 43 determines which of these modes is currently selected (stepS42 of FIG. 12).

[0129] When in the photographic mode, the start photography command isinput from the CPU 43 into the CCD sensor 24 and photography begins.Moreover, the picture image is taken regularly, and since thedescription of the operation for sequential display on the monitor 29was already given in the first and second embodiments, furtherdescription will be omitted here.

[0130] The CPU 43 determines whether the release switch SW1 of theoperation switches 44 has been pressed. If the release switch SW1 ispressed (step S44 of FIG. 12), the following release routine is executed(step S45 of FIG. 12).

[0131] The CPU 43 outputs the stop output command of the analogprojected image signal to the encoder 27. The encoder 27 stops,according to such command, reading the field picture image that isstored in the video memory 39, and temporarily stops the output of theanalog projected image signal to the monitor 29 (step S51 of FIG. 13).Next, at the moment that the release switch SW1 is pressed, the imageformed on the CCD sensor 24 is accumulated and stored to the pictureimage memory 26 through the A/D converter 25 (step S52 of FIG. 13).

[0132] The picture image processing circuit 38 divides the frame pictureimage that is stored in the picture image memory 26 into an even numberfield picture image and an odd number field picture image by reading thepicture element of every other scanning line. The two picture imagefields are transferred to the video memory 39 (step S53 of FIG. 13).

[0133] The CPU 43 outputs the restart output command of the analogprojected image signal to the encoder 27, and the encoder 27 reads theeven number field picture image and the odd number field that are storedin the video memory 39, and D/A converts each of these to the analogprojected image signal, and then outputs it to the monitor 29 (step S54of FIG. 13).

[0134] According to the operation described above, the operator has theability to take in a picture image at the moment there is a photographicopportunity by pressing the release switch SW1.

[0135] Next, a description of the operation that records the takenpicture image into the flash memory 35 will be described. The CPU 43determines whether the recording switch SW2 of the operation switches 44is pressed. When the recording switch SW2 is pressed (step S46 of FIG.12), the following recording routine is executed (step S47 of FIG. 12).

[0136] The picture image processing circuit 41, according to thethumbnail picture image creation command from the CPU 43, reads theframe picture image that is stored in the picture image memory 26, and,as shown in FIG. 17, creates the ¼ reduced-size picture image. Thisreduced-size picture image is a thumbnail picture image for single-viewdisplay use. It is not limited to a ¼ reduction. First, the pictureimage data is extracted from the frame picture image by every otherscanning line. Next, every other picture element from each line ofpicture image data that was extracted is thinned, thereby creating a ¼reduced-size picture image. The thumbnail picture image created from thepicture image processing circuit 41 is mapped to a prescribed address inthe frame memory 42 (step S61 of FIG. 14).

[0137] Next, the picture image processing circuit 41 reads the thumbnailpicture image that is stored in the frame memory 42 and transfers thatto the picture image processing memory 32 (step S62 of FIG. 14).

[0138] The CPU 43, for example, is set in advance so as to compress aseveral MB frame picture image to a target data amount of about 100 KB.In addition, since the thumbnail picture image is the data amount of ¼of the frame picture image, the CPU 43 is set in advance so as tocompress the thumbnail picture image to a preliminary compression targetdata amount of 25 KB. Although the preliminary compression target dataamount is set in advance in the CPU 43, as an alternative, the CPU 43may also be set up to read the data amount of the thumbnail pictureimage and the frame picture image and compute directly by means of theexpression (preliminary compression target data amount)=(target dataamount)×(data amount of the thumbnail picture image)/(data amount of theframe picture image).

[0139] The JPEG circuit 33 repeats the compression process until thethumbnail picture image stored in the picture image processing memory 32is compressed to the preliminary compression target data amount. In thisinstance, a description of the specific numerical value will be givenrelative to the preliminary compress process. For example, the dataamount of the thumbnail picture image becomes 250 KB (with a framepicture image of 1 MB).

[0140] The preliminary compression target data amount and thepreliminary compression initiation command are transferred from the CPU43 to the JPEG circuit 33. The JPEG circuit 33, according to suchcommand, reads the thumbnail picture image that is stored in the pictureimage processing memory 32 and begins the compression. The JPEG circuit33 reads the data amount of the thumbnail picture image that is storedin the picture image processing memory 32 and compresses such dataamount so that it matches the preliminary compression target dataamount. In this instance, since a 250 KB data amount must be compressedso as to become 25 KB, first, compression is performed at a compressionlevel of 30 (expected compression ratio 10%).

[0141] The picture image compression is performed by performing thefollowing steps in the following order: DCT, followed by linearquantization, followed by variable length coding (step S63 in FIG. 14).JPEG circuit 33 repeats the compression by changing the compressionlevel until the compression result is within a range of 25 KB± anallowable value, thereby deriving the compression level when arrivingwithin this range (steps S64 and S65 of FIG. 14).

[0142] For example, when the compression result is 20 KB, since thecompression level is too large and there is the possibility that thepicture image will deteriorate upon reproduction, the compression levelis lowered. According to expression (1) described above, an expectedcompression ratio for the next time is computed to be 12.5%. The JPEGcircuit 33 performs compression again at the compression level thatcorresponds to this expected compression ratio, and it then determineswhether the compression result has become 25 KB.

[0143] In addition, when the compression result is 30 KB, since thecompression level is too small, an expected compression ratio of 8.3% iscomputed by the aforementioned expression (1). Then, the compression isperformed again at the compression level that corresponds to thisexpected compression ratio, and it is determined whether the compressionresult has become 25 KB.

[0144] The change of the compression level is executed by appropriatelyadopting, from a quantization table having different quantizationamounts stored in the internal memory of the JPEG circuit 33, aquantization amount for the desired compression level.

[0145] The JPEG circuit 33 repeats the feed back process describedabove, and the compression level that compresses the thumbnail pictureimage to the preliminary compression target data amount is derived. TheCPU 43 stores that compression level in the internal memory (step S66 ofFIG. 14).

[0146] Next, the picture image processing circuit 41, by means of theframe picture image reading command from the CPU 43, transfers the framepicture image that is stored and accumulated in the picture image memory26 to the picture image processing memory 32 (step S67 of FIG. 14). TheJPEG circuit 33, according to the start main compression command fromthe CPU 43, performs compression by reading the frame picture image fromthe picture image processing memory 32. At this time, the JPEG circuit33, according to the compression level derived by the preliminarycompression, compresses the frame picture image (step S68 of FIG. 14).Since the extent of the spatial redundancy of the frame picture imageand the thumbnail picture image are nearly identical, the compressionlevel of the thumbnail picture image can comply with the frame pictureimage. Accordingly, when compression occurs at this compression level,the frame picture image is compressed to the target data amount.

[0147] The frame picture image that is compressed to the target dataamount is read and recorded to the flash memory 35 through the datatransfer component 34 as a compressed picture image file (step S69 ofFIG. 14). At this time, in the header area of the compressed pictureimage file, together with the identification name of the file, thecompression level at the time of compression as well as theidentification name of the corresponding thumbnail picture image arerecorded.

[0148] According to the operation described above, a taken picture imagecan be recorded to the flash memory 35.

[0149] Next, a description of the operation for reading and reproducingfor display a picture image that has been recorded in the flash memory35 will be provided hereafter. The CPU 43 determines the mode status ofthe mode switch SW5. When switching to the single-view display mode, thesingle-view display routine to be described hereafter is executed (stepS43 of FIG. 12).

[0150] The picture image processing circuit 41, according to thethumbnail picture image reading command from the CPU 43, reads thethumbnail picture image that is stored in the frame memory 42, andtransfers it to the picture image memory 26 (step S71 of FIG. 15). Theencoder 27, according to the stop output command of the analog projectedimage signal from the CPU 43, stops the reading of the field pictureimage from the video memory 39 (step S72 of FIG. 15)

[0151] The picture image processing circuit 38, divides the thumbnailpicture image that is stored in the picture image memory 26 into theeven number field picture image and the odd number field picture imageby reading the picture element of every other scanning line, and thesetwo picture image fields are transferred sequentially to the videomemory 39 (step S73 of FIG. 15). The encoder 27, according to therestart output command of the analog projected image signal from the CPU43, D/A converts the even number field picture image and the odd numberfield picture image of the thumbnail picture image that is stored in thevideo memory 39, and displays it on the monitor 29 that is selected bythe video selection switch 28 (step S74 of FIG. 15). The thumbnailpicture image is displayed on the monitor 29 by means of the operationdescribed above.

[0152] In addition, when the thumbnail selection switch SW6 is pressedin this state, the CPU 43, according to the pressing operation, selectsthe thumbnail picture image (step S75 of FIG. 15). For example, whenthere are 4 thumbnail picture images as shown in FIG. 18, the CPU 43upon each pressing of the SW6, selects the thumbnail picture image inthe sequence of A, then B, then C, then D, and changes exterior framedisplay of the thumbnail picture image that is selected. In this way,following the directions of the CPU 43, the picture image processingcircuit 41 creates the thumbnail picture image by adjusting the exteriorframe of the thumbnail picture image that is selected.

[0153] When turning on the read switch SW3 when the thumbnail pictureimage is in the selected status (step S76 of FIG. 15), the CPU 43, basedon the identification name of the selected thumbnail picture image,reads the corresponding compressed picture image file through the datatransfer component 34 where it is transferred to the picture imageprocessing memory 32 (step S77 of FIG. 16). At this time, the CPU 43reads the compression level at the time of compression from the headerarea of the compressed picture image file.

[0154] The start expansion command and the compression level informationof the compressed picture image file are transferred from the CPU 43 tothe JPEG circuit 33. The JPEG circuit 33 performs the expansion processof the compressed picture image as described previously. At this time,the JPEG circuit 33, for reverse quantization, executes the expansionprocess that corresponds to the compression level used by thequantization table that was used at the time of compression.

[0155] The frame picture image that is expanded is stored andaccumulated in the picture image processing memory 32. The picture imageprocessing circuit 41 transfers such frame picture image to the pictureimage memory 26 (step S78 of FIG. 16).

[0156] The CPU 43 outputs the stop output command of the analogprojected image signal to the encoder 27. The encoder 27 stops thereading of the field picture image from the video memory 39 (step S79 ofFIG. 16). The picture image processing circuit 38 divides the framepicture image of the picture image memory 26 into two fields of pictureimages, and then transfers them to the video memory 39 (step S80 of FIG.16). The encoder 27, in accordance with the restart output command ofthe analog projected image signal from the CPU 43, D/A converts the evennumber field picture image and the odd number field picture image thatare stored in the video memory 39 to a sequential analog projected imagesignal where it is then output to the monitor 29 (step S81 of FIG. 16).

[0157] In accordance with the process described above, the operator can,by selecting the desired picture image from within a group ofsingle-view display thumbnail picture images, reproduce and display suchpicture image onto the monitor 29.

[0158] In this way, in the third embodiment, the compression level isderived by performing preliminary compression on a thumbnail pictureimage for single-view display, and compressing the frame picture imageaccording to such compression level. Accordingly, the compressionprocess for a frame picture image with a large data amount is completedin one attempt, thereby making possible the compression of a framepicture image to a target data amount in a short period of time.

[0159] Moreover, in the present invention, an explanation using anelectronic still camera as the example which employs the picture imagecompression apparatus of the present invention. However, thephotographic component is not a necessary component of the device. Inother words, the present invention may also compress picture image datacreated externally. For example, the compression process may also beapplied to a picture image data read into an image scanner, transferredfrom an external source, or so forth.

[0160] Furthermore, in the present embodiment, a flash memory was usedas the medium to record the compressed picture image. However, withoutbeing limited to that, the invention may also use a magnetic recordingmedium, an optical recording medium, and a magnetooptical recordingmedium, for example. In addition, the picture image compressionprocessing program and the compressed picture image are recorded inindividual recording mediums. They may also be recorded into the samerecording medium.

[0161] Further, in the present embodiment, in the case where the extentof spatial redundancy of the frame picture image and the reduced-sizepicture image is different, there will be cases when the compressionresult of the frame picture image does not match to the target dataamount. At this time, the frame picture image may be compressed directlyso as to match the target data amount. Furthermore, the preliminarycompression target data amount may also be adjusted to correspond toeither target data amount or the compression result of the frame pictureimage, thereby making a match with the target data amount by performingagain preliminary compression followed by compression of the framepicture image.

[0162] Furthermore, any one portion of the frame picture image may alsobe cut-out as the method of creating the reduced-size picture image.

[0163] In addition, in the third embodiment, the thumbnail picture imageitself may also be compressed by the JPEG circuit 33 and recorded intothe flash memory 35. By so doing, the frame memory 42 for the recordingof the thumbnail picture image can be an inexpensive memory such as aDRAM.

[0164] In addition, while the description in the present embodiment usedthe JPEG, MPEG may also be used as the compression method. Various othercompression techniques, such as, for example, wavelet and fractalcompression, can be used with the invention. Rather than Huffman coding,the variable length coding can be, for example, run-length coding, LZW,and/or minimum redundancy coding.

[0165] Although the described embodiments used a CCD as the imagepickup, other photosensors could be used. For example, a CMOS device ora PSD (Photo-Sensitive-Diode) also can be used as the image pickup.

[0166] In the illustrated embodiment, the camera controller (the CPU andassociated circuitry) is implemented using a suitably programmed generalpurpose computer, e.g., a microprocessor, microcontroller or otherprocessor device (CPU or MPU). It will be appreciated by those skilledin the art, that the controller can also be implemented as a singlespecial purpose integrated circuit (e.g., ASIC) having a main or centralprocessor section for overall, system-level control, and separatesections dedicated to performing various different specificcomputations, functions and other processes under control of the centralprocessor section. The controller can also be implemented using aplurality of separate dedicated or programmable integrated or otherelectronic circuits or devices (e.g., hardwired electronic or logiccircuits such as discrete element circuits, or programmable logicdevices such as PLDs, PLAs, PALs or the like). The controller can alsobe implemented using a suitably programmed general purpose computer inconjunction with one or more peripheral (e.g., integrated circuit) dataand signal processing devices. In general, any device or assembly ofdevices on which a finite state machine capable of implementing the flowcharts shown in FIGS. 4-7 and/or 12-16 can be used as the controller.

[0167] As noted earlier, the invention further includes, as anotheraspect, a carrier wave encoded with the control program (describedabove) that is readable by the controller (a computer) to control thecamera to function as described above. The carrier wave can betransmitted over a communications network such as, for example, theWorld Wide Web, and/or transmitted in a wireless fashion, for example,by radio waves or by infrared waves. Additionally, or alternatively, thecarrier wave can be fixed in a computer-readable recording medium, suchas, for example, a CD-ROM, a computer hard drive, RAM, or other types ofmemories that are readily removable or intended to remain fixed withinthe computer. One such memory is the ROM card 45.

[0168] Additionally, and as noted earlier, the invention can beimplemented in apparatus other than a camera. That is, the device thatperforms the image processing need not be capable of creating anelectronic picture image. The electronic picture image simply can beinput to the image processing apparatus.

[0169] While the present invention has been described with reference topreferred embodiments thereof, it is to be Understood that the inventionis not limited to the disclosed embodiments or constructions. To thecontrary, the invention is intended to cover various modifications andequivalent arrangements. In addition, while the various elements of thedisclosed invention are shown in various combinations andconfigurations, which are exemplary, other combinations andconfigurations, including more, less or only a single element, are alsowithin the spirit and scope of the invention.

What is claimed is:
 1. A picture image compression apparatus thatcompresses data of a picture image to a predetermined target dataamount, comprising: picture image creation means for creating, from thepicture image, a reduced-size picture image having a reduced number ofpicture elements of the picture image; preliminary compression means forderiving a compression level that compresses the reduced-size pictureimage to a preliminary compression target data amount that is related tothe predetermined target data amount; and compression means forcompressing the data of the picture image to the predetermined targetdata amount using the compression level derived by the preliminarycompression means.
 2. The picture image compression apparatus of claim1, wherein the picture image creation means creates a field pictureimage as the reduced-size picture image.
 3. The picture imagecompression apparatus of claim 1, wherein the picture image creationmeans creates a thumbnail picture image as the reduced-size pictureimage.
 4. The picture image compression apparatus of claim 3, wherein aplurality of the thumbnail picture images are capable of being displayedin a single-view display.
 5. The picture image compression apparatus ofclaim 1, wherein the preliminary compression means derives thecompression level by repeatedly compressing the reduced-size pictureimage using different compression levels until a compression level isused that results in the preliminary compression target data amountbeing obtained.
 6. The picture image compression apparatus of claim 1,wherein the preliminary compression means and the compression meansperform compression by omitting redundant data from the picture imageand the reduced-size picture image.
 7. The picture image compressionapparatus of claim 1, further comprising data amount determination meansfor deriving the preliminary compression target data amount from thepredetermined target data amount.
 8. The picture image compressionapparatus of claim 7, wherein the data amount determination means alsoderives the preliminary compression target data amount from a ratiobetween data amounts of the picture image and the reduced-size pictureimage.
 9. The picture image compression apparatus of claim 1, whereinthe picture image compression apparatus is an electronic camera havingpicture image input means for photoelectrically converting an objectimage into the data of the picture image.
 10. The picture imagecompression apparatus of claim 1, wherein the preliminary compressiontarget data amount is less than the predetermined target data amount.11. A picture image compression apparatus that compresses data of apicture image to a predetermined target data amount, comprising: apicture image processor that creates, from the picture image, areduced-size picture image having a reduced number of picture elementsof the picture image; a compression circuit; and a controller that usesthe compression circuit to derive a compression level that compressesthe reduced-size picture image to a preliminary compression target dataamount that is related to the predetermined target data amount, thecontroller then using the compression circuit to compress the data ofthe picture image to the predetermined target data amount using thederived compression level.
 12. The picture image compression apparatusof claim 11, wherein the picture image processor creates a field pictureimage as the reduced-size picture image.
 13. The picture imagecompression apparatus of claim 11, wherein the picture image processorcreates a thumbnail picture image as the reduced-size picture image. 14.The picture image compression apparatus of claim 11, wherein thecompression circuit performs compression by omitting redundant data fromthe picture image that is to be compressed.
 15. The picture imagecompression apparatus of claim 14, wherein the compression circuit is aJPEG compression circuit.
 16. The picture image compression apparatus ofclaim 11, wherein the picture image compression apparatus is anelectronic camera having a photoelectric converter that converts anobject image into the data of the picture image.
 17. The picture imagecompression apparatus of claim 11, wherein the preliminary compressiontarget data amount is less than the predetermined target data amount.18. A method of determining a compression level to be used to compressdata of a picture image to a predetermined target data amount,comprising the steps of: creating, from the picture image, areduced-size picture image having a reduced number of picture elementsof the picture image; and deriving the compression level by compressingthe reduced-size picture image to a preliminary compression target dataamount that is related to the predetermined target data amount.
 19. Themethod of claim 18, further comprising the step of compressing the dataof the picture image to the predetermined target data amount using thederived compression level.
 20. The method of claim 18, wherein thereduced-size picture image is a field picture image.
 21. The method ofclaim 18, wherein the reduced-size picture image is a thumbnail pictureimage.
 22. The method of claim 18, wherein the step of deriving thecompression level includes repeatedly compressing the reduced-sizepicture image using different compression levels until a compressionlevel is used that results in the preliminary compression target dataamount being obtained.
 23. The method of claim 18, further comprisingderiving the preliminary compression target data amount from thepredetermined target data amount.
 24. The method of claim 23, whereinthe preliminary compression target data amount also is derived from aratio between data amounts of the picture image and the reduced-sizepicture image.
 25. The method of claim 18, wherein the preliminarycompression target data amount is less than the predetermined targetdata amount.
 26. A computer-readable data signal embodied in a carrierwave, the data signal encoded to transmit a control program fordetermining a compression level to be used to compress data of a pictureimage to a predetermined target data amount, the control programincluding instructions for: creating, from the picture image, areduced-size picture image having a reduced number of picture elementsof the picture image; and deriving the compression level by compressingthe reduced-size picture image to a preliminary compression target dataamount that is related to the predetermined target data amount.
 27. Thedata signal of claim 26, wherein the control program further includesinstructions for compressing the data of the picture image to thepredetermined target data amount using the derived compression level.28. The data signal of claim 26, wherein the creating instruction is tocreate the reduced-size picture image by creating a field picture image.29. The data signal of claim 26, wherein the creating instruction is tocreate the reduced-size picture image by creating a thumbnail pictureimage.
 30. The data signal of claim 26, wherein the instruction toderive the compression level includes an instruction to repeatedlycompress the reduced-size picture image using different compressionlevels until a compression level is used that results in the preliminarycompression target data amount being obtained.
 31. The data signal ofclaim 26, further comprising an instruction to derive the preliminarycompression target data amount from the predetermined target dataamount.
 32. The data signal of claim 31, wherein the preliminarycompression target data amount also is derived from a ratio between dataamounts of the picture image and the reduced-size picture image.
 33. Thedata signal of claim 26, wherein the preliminary compression target dataamount is less than the predetermined target data amount.
 34. The datasignal of claim 26, including a computer-readable recording medium onwhich the carrier wave is recorded.
 35. A method for compressing a dataamount of picture image data of a picture image acquired by an imagepickup device, to a predetermined target data amount, comprising:creating a reduced-size picture image from the picture image by reducinga number of picture elements of the picture image; and deriving acompression level for compressing the picture image data by compressinga data amount of the reduced-size picture image to a preliminarycompression target data amount.
 36. A method for compressing a dataamount of picture image data of a picture image acquired by an imagepickup device to a predetermined target data amount, comprising:generating the picture image data from the picture image; creating areduced-size picture image from the picture image data by reducing anumber of picture elements of the picture image data; and deriving acompression level for compressing the picture image data by compressinga data amount of the reduced-size picture image to a preliminarycompression target data amount.